Alkyation process



Patented Sept. 24, 1946 ALKYATION PROCESS Jacob R. Meadow, Lexington, Ky., assignor to Socony-Va'cuum Oil Company, Incorporated, a corporation of New York No Drawing. Original application October 9,

1943, Serial No. 505,661. Divided and this application May 23, 1945, Serial No. 595,492

Claims. (o1. zoo-683.45

This invention relates to the alkylation of parafiinic hydrocarbons with olefinic hydrocarbons, and is more particularly concerned with the catalytic alkylation of isoparafiinic hydrocarbons with olefinic hydrocarbons in the presence of hydrofluoric acid. It is well known in the art to eifect the union of paraifinic hydrocarbons and olefinic hydrocarbons by processes broadly called alkylation processes. In alkylation processes, a charge including a mixture of a paraifinic hydrocarbon called the parafiinic reactant, and an olefinic hydrocarbon called the olefinic reactant, is introduced into a reaction zone under suitable reaction conditions of temperature and pressure, referred to as alkylating conditions, to yield a product called the hy-. drocarbon alkylate, which comprises constituents of a saturated character. Since the alkylating conditions cause also polymerization of the olefinic reactant, it is necessary to maintain a relatively low concentration of the olefinic reactant in the charge. Generally speaking, the more severe the alkylating conditions, i. e. the higher the temperatures and pressures, the higher the Yield of hydrocarbon alkylate. The only limit'to the pressure used appears to be the feasibility of maintaining high pressures. "On the other hand, the temperature used is limited by the degradation of the hyqdrocarbo-n reactants in the charge to low molecular weight hydrocarbons, and the occurrence of secondary reactions, including polymerization of the olefinic reactant, under high temperature conditions, that substantially reduce the purity of the product obtained,

Alkylation may be conducted at high temperatures and pressures, on the order of over 900 F. and over 4000. pounds per square inch, respectively; ormay be carried out at lower temperatures and pressures, in the presence of substances that facilitate the union of parafiinic hydrocarbons and olefinic hydrocarbons, hence called alkylation catalysts, thereby assuring a high yield alkylation of paraifinic hydrocarbons with ole-' finic hydrocarbons in the presence of alkylation catalysts consisting essentially of metal and nonmetal halides, such as aluminum chloride, boron 2 trifluoride and the like, of sulfuric acid, of phosphoric acid, of metal phosphates, of activated clays, and the like. In these processes, the alkylation catalysts are used in amounts varying between about 10% and 200% by weight, on the charge, depending upon the alkylation catalyst and conditions used. However, it would seem that these and similar alkylation catalysts have one or more definite disadvantages, among which the most important are promotion of the aforementioned secondary reactions and loss oi? alkylation catalytic activity on the part of the catalyst, relatively rapidly. Notably, the metal halides form additional compounds with olefinic reactants, that ultimately degenerate into tarry masses that represent loss of catalytic activity of the alkylation catalysts and loss of potential olefinic reactant. Similarly, sulfuric acid causes the formation of various organic compounds that ultimately reduce the catalytic activity of the acid necessitating periodic removal of the sulfuric acid contaminated with thesecompounds, and replacement with fresh acid. It must be noted further, that sulfuricacid'is a powerful oxidizing agent and its use, at temperatures above about E, entails extensive undesirable secondary reactions that consume the acid and the valuable hydrocarbon reactants. I V

Concentrated hydrofluoric acid, when used as an alkylation catalyst, apparently does not have these disadvantages. It is a non-oxidizingand non-reducing substance and hence, it may be used at elevated temperatures without any of the undesirable results referred to hereinbefore. Several processes are known in the art for catalytically alkyiating parafiinic hydrocarbons with olefinic hydrocarbons in the presence of hydrofluoric acid. Generally speaking, the process is carried out with the hydrocarbon reactants substantially in liquid phase and in the presence of sufficient amounts of hydrofluoric acid to effect substantial saturation of thehydrocarbon liquid referred to. Thus, it is known to effect the alkylation of paraffinic hydrocarbons with olefinic hydrocarbons in the presence of alkylation catalysts consisting of mixtures of sulfuric acid and hydrofiuoric acid, or of mixtures of sulfuric acid and hydrochloric or hydrobromic acids, or of mixtures of a metal halide It is also known that certain substances called promoters, promote .the catalytic action of aland the corresponding I hydrogen halide. v

fluorides, or of elemental halogens, excluding fluorine.

It is an object of the present invention to provide an efficient process for catalytically alkylating parafilnic hydrocarbons with olefinic hydrocarbons. Another object of the present invention is to provide an efficient process for catalytically alkylating paraflinic hydrocarbons with olefinio hydrocarbons in the presence of hydrofluoric acid. A more specific object is to provide a process for catalytically alkylating parafiinic hydrocarbons with oleflnic hydrocarbons to produce high yields of high-octane blending agents for the manufacture of improved motor fuels. A very important object of the present invention is to afford a process capable of carrying out the above objects by carrying out the reaction in the presence of halogens, other than fluorine, or of halogen compounds, other than fluorides. Other objects and advantages of the present invention will become apparent to those skilled in the art from the following description.

Broadly stated, the present invention provides a process for alkylating paraflim'c hydrocarbons with olefim'c hydrocarbons, which comprises contacting a paraffinic hydrocarbon and an olefinic kylate, when these compounds or elemental halogens are added to the hydrogen fluoride, before the alkylation operation is carried out.

When a mixture of a parafflnic hydrocarbon, particularly a low-boiling isoparaflinic hydrocarbon such as isobutane, anhydrous or concentrated hydrofluoric acid, and an olenfinic hydrocarbon such as isobutylene, is maintained at a reduction temperature, a union takes place between the parafiinic hydrocarbon and the oleflnic hydrocarbon to produce a higher boiling paraflinic hydrocarbon which generally represents structurally, the addition of the original hydrocarbon reactants. Valuable high-octane blending agents for the manufacturing of improved motor fuels may be thus produced. For example,

H3 H CH3 CH3 H CH3 l l 2 H l CH3(IJH (3 CH3 CHaC- -CH3 CH3 H CH3 H Isobutane Isobutylene Isooctane In carrying out the alkylation of paraflinic hydrocarbons with olefinic hydrocarbons in the presence of hydrofluoric acid as alkylation catalyst, the hydrofluoric acid should be used in amounts of at least about and up to about pressure.

60% of the total charge, on a liquid volume basis. Aqueous solutions of hydrofluoric acid in Which hydrogen fluoride is present in concentrations greater than may be used, but the use of to hydrofluoric acid is to be preferred, and substantially anhydrous hydrofluoric acid or hydrogen fluoride is very effective aSan alkylation catalyst in the process of my invention.

The reaction temperature may be varied over a wide range depending upon the parafflnic reactant used in the reaction. Generally speaking the temperature of reaction varies between about 0 F. and about 400 F., lower temperatures being used when the more reactive paraflimc or oleflnic reactants are employed and higher temperatures becoming necessary when the less reactive paraffinic or oleflnic reactants are employed. For instance, when the paraffinic reactant is isobutane or isopentane, and when the oleflnic reactant is propylene or butylene, alkylation may be readily effected at temperatures varying between about 35 F. and about 100 F.

Ordinarily, alkylation in the presence of hydrofluoric acid as the alklation catalyst, is carried out under super atmospheric pressure, and pressures varying between about 20 pounds per square inch and 500 pounds per square inch have been found ample in most instances. rule, the most suitable pressure is more or less dependent upon the particular temperature involved and when high temperatures are employed, pressures as high as 2000 pounds per square inch may be employed, if desired.

In carrying out alkylation of paraflinic hydrobons with olefinic hydrocarbons, it is well known, as stated hereinbefore, to maintain a relatively low concentration of the olefinic reactant in the reaction zone, in order to preclude extensive polymerization of the oleflnic hydrocarbon. Accordingly, it is advisable to maintain the olefinic hydrocarbon concentration in the reaction zone below about 25% by volume, and preferably, be-

.tween about 7% and about 12% by volume. In

continuous operation, this is effected by introducing the olefinic reactant over a period of time corresponding to the reaction period.

The reaction period duringwhi-ch the oleflnic reactant is introduced into the reaction zone to react with the paraffinic reactant to produce the hydrocarbon alkylate, depends upon the temperature, and to a certain extent, upon the Ordinarily, a reaction period varying between 15 minutes and 2 hours is satisfactory. At higher temperatures, the time of reaction may be as low as 5 minutes and even lower, while at lower temperatures, the time of reaction may be as high as 5'hours.

It must be understood, that the reaction variables are more or less interdependent, hence when one is arbitrarily fixed, the limits within which the others may bejvaried, are somewhat restricted. In any particular instance, the most desirable conditions can be'readily ascertained by one skilled in the art, the preferred ranges of these variables having been indicated hereinbefore. The paraffinic and. olefinic hydrocarbons to be used in my process may be derived from any suitable source, as is well known in the art, and may be usedeither in the pure state or in admixture with other constituents not undesirable. The

,paraffinic and olefinic hydrocarbons usually em- As a general tration of parafiinic hydrocarbons to 2.

ethane, and the normally gaseous olefinlc hydrocarbons, propylene, butylene and pentene, as

is well understood in the art. A conventional and preferred source of parafiinic and olefinic hydrocarbons is the fixed gases obtained around petro- 5 leum refineries. .These fixed gases may furnish substantially all the desired paraflinic and olefinic hydrocarbons, or it may be necessary or desirable to obtain additional supplies, as is well understood. Additional olefinic hydrocarbons, if required, may be formed from a portion of the paraflinic hydrocarbons. On the other hand,

' additional amounts of parafiinic hydrocarbons may be admixed in order to increase the concendesired magnitude.

5% and ab.out'50% with respect to the amount of hydrogen fluoride employed. appear to be unnecessary; however, it must be noted thatthey may be employed if desired, al-

Larger' amounts though no additional advantages result therefrom. The amounts of hydrogen fluoride addi- Runl B11112 Run3 um Isobutane, weight in grams Isobutylene, weight in grams Hydrogen fluoride, weight in grams Hydrogen fluoride additive, weight in gram Temperature, 0 Pressure in pounds per square inch Hydrocarbon alkylate, weight in grams Total octanes 90 C.l 0., weight in grams.

Isooctane 98 O.101 0., weight in grams 39 T butyl-bromide 18.

The organic and inorganic halides, other than fluorides, and the elemental halogens, other than fluorine, that are used in accordance with the process of my invention, may be solids, liquids or gases under normal conditions. It is suspected that the improved results obtained with those substances, is probably due more to an ultimate activation of the olefinic reactant during the alkylation operation, than to promoter action on the hydrogen fluoride catalyst, although the latter should not be excluded'altogether. Whatever the function of these substances is, the quality and quantity of the hydrocarbon alkylate 40 are substantially improved through their use. In view of the relative uncertainty ofthe' n'iinner in which these substances'function during the alkylation operation, these substances may be referred to more correctly, as hydrogen fluoride additives, rather than as promoters or as activators.

The hydrogen fluoride additives of my invention include various metallic chlorides, bromides and iodides, for example, anhydrous calcium chloride; organic halogen compounds, excepting fluorides, such as alkyl chlorides, bromides and iodides, especially secondary and tertiary halides; aralkyl halogen compounds, excepting fluorides; aliphatic and aromaticiacid chlorides, bromides and iodides; non-metallic halides, excepting fiuorides, such as phosphorus and sulfur chlorides, bromides and iodides; hydrogen halides, excepting of course hydrofluoric acid; and finally, the. halogens themselves, excepting fluorine.

I especially prefer to use, as hydrogen fluoride additives, alkyl chlorides and bromides, particularly tertiary alkyl chlorides and bromides and secondary alkyl chlorides and bromides, hydrogen halides other than hydrofluoric acid, and halogens other than fluorine. Specific and preferred hydrogen fluoride additives that may be mentioned by way of non-limiting examples are: tertiary butyl chloride, tertiary butyl bromide, tertiary amyl chloride, tertiary amyl bromide, iso- 7 propyl chloride, isopropyl bromide, propylene chloride, propylene bromide, hydrogen chloride, hydrogen bromide, chlorine and bromine.

The amounts of hydrogen fluoride additives ordinarily used in my process, vary between about The octane fraction of the hydrocarbon alkylate produced by my proces contains 2,2,4-tri methylpentane in predominant amounts, and the results of infra-red analysis indicate the presence also of 2,3,3-trimethylpentane. This octane is not present in the hydrocarbon alkylates obtained when the alkylation is conducted in the absence of my hydrogen fluoride additives and under the conditions outlined hereinbefere. Infra-red analyses also indicate that the hydrocarbon alkylate obtained when alkylation is carried out in the absence of the hydrogen fluoride additives of my invention and under conditions outlined in the preceding table, contain appreciable concentrations of unsaturates whichare not present in the hydrocarbon alkylates obtained in the process of my invention.

The present application is a division of copending application Serial Number 505,661, filed October 9, 1943. I The present invention may be embodied in other specific forms without departing from the spirit or essential attribute thereof, and it is therefore desired that the present embodiments be considered in all respects as illustrative and not restrictive, reference being had to the appended claims rather than to the foregoing description to indicate the. scope of the invention.

I claim:

1. In a process for alkylating a paraffinic hydrocarbon having at least three carbon atoms with an olefinic hydrocarbon having at least three carbon atoms, which includes contacting said paraffinic hydrocarbon with said olefinic hydrocarbon in a reaction zone under alkylating conditions, in the presence of a hydrogen fluoride alkylation catalyst, and maintaining said paraffinic hydrocarbon in excess over said oleflnic hydrocarbon in said reaction zone so that alkylation is the principal reaction; the improvement which comprises contacting said parafiinic hydrocarbon and said olefinic hydrocarbon with a hydrogen fluoride alkylation catalyst in said reaction zone, in the presence of a material selected from the group consisting of chlorine, bromine,

and iodine. I

2; The process of manufacturing high-octane gasoline, which'comprises contacting a normally gaseous isoparafiinic hydrocarbon and a normally gaseous olefinic hydrocarbon having at least three carbon atoms in a reaction zone under alkylating conditions, with a hydrogen fluoride alkylation catalyst, in the presence of ch10- rine, and maintaining said normally gaseous isoparaflinic hydrocarbon in excess over said normally gaseous olefinic hydrocarbon in said reaction zone so that alkylation is the principal reaction.

3. The process of manufacturing high-octane gasoline, which comprises contacting a normally gaseous isoparamnic hydrocarbon and a normally gaseous olefinic hydrocarbon having at least three carbon atoms in a reaction zone under alkylating conditions, with a hydrogen fluoride alkylation catalyst, in the presence of bromine, and maintaining said normally gaseous isoparaffinic hydrocarbon in excess over said normally gaseous olefinic hydrocarbon in said reaction zone so that alkylation is the principal reaction.

4. The process of manufacturing high-octane gasoline, which comprises contacting isobutane and isobutylene, in a reaction zone under alkylating conditions, with a hydrogen fluoride alkylationcatalyst, in the presence of chlorine, and maintaining said isobutane in excess over said isobutylene in said reaction zone, so that alkylation is the principal reaction.

5. The process of manufacturing high-octane gasoline, which comprises contacting isobutane and isobutylene, in a reaction zone under alkylating conditions, with a hydrogen fluoride alkylation catalyst, in'the presence of bromine, and maintaining said isobutane in excess over said isobutylene in said reaction zone, so that alkylation is the principal reaction.

JACOB R. MEADOW. 

